Screed for clearing nose of tilting vessel

ABSTRACT

An elongated screed bar, the end of which is secured to the concrete support columns for a basic oxygen furnace vessel, and positioned to scrape the skull from the vessel mouth as the vessel is tilted to dump the slag therefrom.

United States Patent 1 Pineura, Jr. et al.

[111 3,747,910 [4 1 Jul 24, 1973 SCREED FOR CLEARING NOSE 0F TILTING VESSEL [75] Inventors: Peter P. Pincura, Jr., Amherst; Luis T. Sanchez, Lorain, both of Ohio [7 31 Assignee: United States Steel Corporation, Pittsburgh, Pa.

[22] Filed: Aug. 4, 1971 [21] App]. N0.: 168,936

[52] US. Cl. 266/1 S [51] Int. Cl. C2lc 5/46 [58] Field of Search 266/1 S [56] References Cited UNITED STATES PATENTS 3,197,187 7/1965 Lakin et al. 266136 P 3,335,445 8/1967 Kinzler 266/1 S Primary Examiner-Gerald A. Dost Att0meyForest C. Sexton [57] ABSTRACT An elongated screed bar, the end of which is secured to the concrete support columns for a basic oxygen furnace vessel, and positioned to scrape the skull from the vessel mouth as the vessel is tilted to dump the slag therefrom.

3 Claims, 4 Drawing Figures PATENTED Jul 24 I973 SHEET 1 BF 2 PATENIEDJULZMQTS SHEEI 2 OF 2 SCREED FOR CLEARING NOSE OF TILTING VESSEL BACKGROUND OF THE INVENTION The manufacture of steel in the basic oxygen furnace involves blowing oxygen gas into molten iron to burn the impurities therefrom. The reaction is at times violent enough to cause considerable slopping or turbulence in the bath whereby drops of metal and slag are thrown from the molten bath and out of the vessel. This frequently causes metal and slag called a skull, to form on the cooler lip or mouth outside of the steelmaking vessel. In order to continue efficient operation of the furnace, the skull must not be allowed to grow appreciably. That is, excessive accumulation of metal and slag around'the furnace mouth will cause several operating difficulties, such as interference with hot metal and scrap charging, metal spillage when tapping, increased gas velocities through the mouth and therefore enchanced slopping, reduction in lining life, damage to vessel drives, and extensive delays in removing the accumulated skull as well as possible damage to the vessel shell during skull removal.

Since the industry is well aware of the above problems, many devices have been developed to remove the skull before there is substantial accumulation. Most of these devices comprise a portable device having an arcuate row of steel teeth spaced along a support member and so positioned such that when the vessel is tilted to tap the charge, the mouth thereof will pass adjacent to the steel teeth which scrape the skull accumulation therefrom. Although such devices have met with some degree of success, there are still many problems associated therewith. For example, fragments of the skull frequently become lodged between the steel teeth and thus interfere with vessel clearance adjacent to the teeth. In many installations the scraping teeth and supporting structure are fixed to the charging floor structure which is independent of the vessel supporting structure. The downward thrust of the vessel against such devices will eventually damage the floor structure. The portable nature of some devices does not provide sufficient rigidity to be completely effective. Because of slight relative movement between the two supporting structures, proper clearance between vessel and scraping teeth is difficult to maintain. Still other problems are encountered when a skull or a portion thereof is so firmly welded to the vessel mouth that it is not readily dislodged. Forcing such a welded skull against the scraper teeth will often damage the vessel itself or the vessel tilting mechanism or break the vessel scraping teeth. Indeed, mechanical scrapers have been developed which incorporate automatic release mechanisms which will disengage the scraper teeth when the scraping forces thereagainst exceed a predetermined maximum value. Although such mechanisms have been successful in preventing damage to the scraper mechanism and more importantly in preventing damage to the vessel and vessel tilting mechanism, these scraping devices are complex and expensive, and indeed are not effective in removing such skulls or portions thereof which are firmly welded to the vessel mouth.

SUMMARY OF THE INVENTION This invention ispredicated upon our conception and development of a simplified but yet more effective means for scraping the mouth of a basic oxygen furnace to remove the skull therefrom.

An object of this invention is to provide a simplified and improved means for removing the skull and skull fragments from the mouth of a basic oxygen furnace which substantially overcomes the above disadvantages.

Another object of this invention is to provide an inexpensive means for removing theskull from a basic oxygen furnace which is secured to the furnace support columns to assure a positiveinterference to the skull without damage to the charging floor structure, and which lacks sufficient rigidity to damage the vessel or vessel tilting mechanism in the event a welded skull is encountered.

A further object of this invention is to provide a means for removing the skull from a basic oxygen furnace which can be utilized in a matter of seconds after each heat without loss of operating time and thereby preventing a build-up or accumulation of skulls that could become damaging when ultimately removed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational front view of a basic oxygen furnace incorporating the skull removing apparatus of this invention. The furnace vessel is shown in a semitilted position.

FIG. 2 is a sectional side view of the furnace and apparatus shown in FIG. 1.

FIG. 3 isan elevational side view of the screed bar retaining means taken along the line III-III of FIG. 2; and

FIG. 4 is a perspective view of the screed bar.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the drawings, particularly FIGS. 1 and 2, a conventinoal basic oxygen furnace is employed having a vessel 10 rotatably mounted at trunnions 12 between a pair of concrete support columns 14. Since basic oxygen furnaces are well known in the art, further details thereof are not necessary here.

The skull removing apparatus of this invention simply comprises an elongated steel screed bar 20 rigidly secured in a horizontal position to the concrete support columns 14. The screed bar 20 is positioned such that the opening or mouth of vessel 10 will just clear the bar 20 as vessel 10 is sufficiently rotated about trunnions 14 to dump the slag therein. The center part of screed bar 20 is bent arcuately away from vessel 10 to provide an arcuate contact surface so that a uniform clearance is maintained around the full circumference of the mouth on vessel 10 as vessel 10 is rotated past screed bar 20.

With reference to FIG. 3, screed bar 20 is rigidly held in place against the forward edge of concrete support columns 14 by a pair of U-brackets 22. In order to provide suitable adjustment of screed bar 20 relative to vessel 10, brackets 22 are substantially wider than necessary for retaining screed bar 20 alone. Accordingly, a plurality of plate shims 24 are inserted on both sides of screed bar 20 to fill the space between screed bar 20 and brackets 22. Screed bar 20 can therefore be adjusted towards or away from vessel by merely removing a suitable number of shims 24 from one side of screed bar 20 and reinserting them on the other side of bar 20. Shim pack cover plate (not shown) may be employed to keep the shims in place.

In operation, vessel 10 is in the upright position while the heat therein is being blown. When the heat is finished, the vessel 10 is first tilted in one direction to drain the molten metal through a tap hole (not shown) in the upper side thereof. After the metal has been tapped, the vessel 10 is tilted in the opposite direction to drain the slag therefrom through the mouth of vessel 10 and into a slag pot 26. It is during this slag draining operation that the vessel mouth is cleaned by screed bar 20.

At first glance, the skull removing apparatus of this invention does not appear to differ significantly from other prior art skull removing devices. Specifically, in our apparatus as well as many other prior art devices, skull removal is effected merely by rotating the vessel to a point where the mouth thereof passes adjacent to a screed member which scrapes or knocks the skull therefrom. As noted previously, however, the prior art has experienced considerable difficulty with such skull removers, in that damage thereto, to the charging floor, or to the vessel or vessel tilting mechanism, may result if a skull is encountered which is not readily loosened from the vessel. In view thereof, the prior art has directed its attention to more complicated devices incorporating hydraulic or other automatic release systems which will disengage the skull remover when the forces thereagainst exceed predetermined limits. The fixed skull removing apparatus of this invention provides the same advantages without the complicated automatic release mechanisms.

Specifically, the screed bar 20 of our invention is not secured to the charging floor or floor structure, or to any other relatively light structure which can be damaged. Rather, our screed bar 20 is secured to the concrete vessel support columns 14, which are quite massive and rigid and cannot therefore be damaged. Since basic oxygen vessels are extremely heavy and rotatable, the concrete support columns are necessarily massive and rigid. Therefore, screed bar 20, which is rigidly secured to such massive support columns will provide a positive interference to any skull material on the mouth of vessel 10.

In addition, the screed bar 20 of our apparatus is rather long, and is rigidly supported only at the extreme ends thereof. Therefore, screed bar 20 is somewhat flexible to forces applied midway between the supports. Therefore, should screed bar 20 encounter a skull or skull fragment which is firmly welded to the mouth of vessel 10, the screed bar 20 will be deflected away thus avoiding damage to the vessel 10 or vessel tilting mechanism. Such a skull may be eventually loosened by repeated contact with screed bar 20. If not, then other means must be employed to remove the skull. Nevertheless, since the skull build-up will most likely be rather small, since the only accumulation will be that resulting from one heat, any deflection of screed bar 20 will likely be within the elastic limits of the bar 20. Therefore, if screed bar 20 is deflected by a welded skull, it will spring back to its original position once the skull has passed. Even if the screed bar 20 is permanently bent out of shape, it is easily repaired and replaced in comparison with damage repairs resulting from piror art skull removing devices. 0f most importance, however, is the fact that damage to the vessel 10 of vessel tilting mechanism is avoided, since the damage, if any, is limited to the inexpensive screed bar 20.

Another advantage enjoyed by our inventive skull remover is that it is utilized after every heat without any positive effort by the furnace personnel. That is to say, the prior art skull removing devices have all been portable in nature requiring activiation, i.e., swinging,pivoting or rolling it into operating position. Because of this effort, the usual practice is to use the device only after an appreciable amount of skull has been allowed to accumulate. With our device, however, no effort is required by the furnace personnel and it is necessarily utilized after every single heat. This provides the additional advantage that the skull is not allowed to accumulate, and hence only a small amount of skull material is removed at a time. This serves to minimize the possibility of damage to the screed bar 20.

To exemplify more specific details of this invention, we have successfully employed the above described embodiment on a 220 ton basic oxygen vessel using a screed bar 20 measuring about 28 feet in length and having a cross-section of 15 inches by 8 inches. The centers of the bar supports, i.e., U-brackets 22, were 26 feet apart, and positioned to provide about 2 inches clearance between the vessel mouth and bar 20. The above dimensions do provide a good combination of rigidity and flexibility. That is, the bar is sufficiently rigid to remove ordinary skull accumulation without difficulty, and yet sufficiently flexible that the bar will be deflected, if a particularly tough skull is encountered, without damage to the vessel 10 or vessel tilting mechanism.

For shims, we have provided four shim packs each being 6 inches thick. The combination we have preferred is one 2 inch plate, two 1 inch plates, two A inch plates and four /4 inch plates. U-brackets 22 are therefore wide enough to accommodate two 6 inch shim packs and the screed bar 20.

We claim:

1. In a basic oxygen furnace for making steel having a vessel mounted to rotate on a horizontal axis between a pair of concrete support columns, apparatus for removing skulls from the mouth of said vessel comprising an elongated screed bar mounted horizontally between said concrete support columns and positioned close to the path of the mouth of said vessel as said vessel is rotated for deslagging after each heat, said screed bar being supported only at the extreme ends thereof and having a cross-section sufficient to provide flexibility so that the screed bar is deflected without damage to the vessel in the event a skull is not dislodged upon initial contact.

2. An apparatus according to claim 1 in which the center portion of said screed bar is bent arcuately away from said vessel to provide an arcuate contact surface so that a uniform clearance is maintained around the full circumference of the vessel mouth.

3. An apparatus according to claim 1 in which the ends of said screed bar are held in place by a pair of U- brackets, said U-brackets being sufficiently oversized to accommodate a plurality of shim plates in addition to the screed bar ends to provide adjustment for positioning said screed bar relative to said vessel. 

1. In a basic oxygen furnace for making steel having a vessel mounted to rotate on a horizontal axis between a pair of concrete support columns, apparatus for removing skulls from the mouth of said vessel comprising an elongated screed bar mounted horizontally between said concrete support columns and positioned close to the path of the mouth of said vessel as said vessel is rotated for deslagging after each heat, said screed bar being supported only at the extreme ends thereof and having a crosssection sufficient to provide flexibility so that the screed bar is deflected without damage to the vessel in the event a skull is not dislodged upon initial contact.
 2. An apparatus according to claim 1 in which the center portion of said screed bar is bent arcuately away from said vessel to provide an arcuate contact surface so that a uniform clearance is maintained around the full circumference of the vessel mouth.
 3. An apparatus according to claim 1 in which the ends of said screed bar are held in place by a pair of U-brackets, said U-brackets being sufficiently oversized to accommodate a plurality of shim plates in addition to the screed bar ends to provide adjustment for positioning said screed bar relative to said vessel. 